She won't buy more useless diet products if you persuade her it's a waste of time. There's only so many times someone can do that, before the message finally sinks in, that noboy is going to create some sort of B.S pill, or fad diet, that will yield amazing physical results.
There's a product out now in Britain, being advertised by some woman who's thin, claiming to have the best Legs of her life after 5 kids.
I forget the name, but all you do is stand on it and slide your Legs apart a bit, then slide them back. The claim is 60 seconds of that a few times a day, will give you Legs like hers.
It just won't, i seriously won't, especially when the product is being marketed without even having the slogan, "must be used as part of a healthy, calorie controlled diet". So it comes across as a magic cureall for Fat legs, presumably in the hope you will not notice her flat stomach and thin Arms, because you're two busy looking at her stick Legs move side to side a little bit, without any actually bending or flexing of any Leg muscles.
Frankly save the money and just do that movement, by standing on a couple of rubber bands and move each Leg alternatiely side to side, because that will create a better range of motion than she gets on her dumb Leg device. Around 35-45 degrees, as opposed to her scenario where it's both Legs together at about 7.5 degrees range of motion per leg, or some other inneffective, pissy angle